Suture needles for medical use are manufactured through processes, such as pressing a stainless steel wire rod having a predetermined diameter, which is formed typically through a drawing process, into a predetermined external shape, cutting it into a predetermined length, grinding each of them to form a sharpened part, forming a thread attaching part, bending the entirety into a half arc shape, and subjecting it to a finishing treatment.
The suture needle for medical use may be a polygonal needle with a polygonal cross section mainly used for suturing skin, or a round needle with a round cross section mainly used for suturing blood vessels and internal organs.
The polygonal needle, a triangular suture needle having a triangular cross section, for example, is formed as follows. First, a round-bar material is formed into a triangular prism shape using a press mold while leaving the needle base as is. The press mold used for this formation is divided into an upper mold and a lower mold, where the lower mold forms a V-shaped groove and two sides of a triangular prism, and the upper mold forms the remaining side of the triangular prism-shaped part with a flat surface. The pressed material has the thread attaching part on the needle base side left as a round bar and the other end made into a triangular prism-shaped part. With the triangular suture needle, three sides of the triangular prism-shaped part are ground to sharpen the tip so as to facilitate insertion of the suture needle into a living tissue and reduce thrust resistance when inserting.
FIG. 9 is an oblique perspective of an exemplary conventional triangular suture needle. A triangular suture needle 10 shown in this diagram has a hole 12 formed in one base end 11a of a thread attaching part 11 using such as a laser. A suture thread 20 is inserted in the hole 12 and calked and fixed.
The part from the thread attaching part 11 of the triangular suture needle 10 to the tip, which is formed into a triangular prism by pressing, is ground to form a sharp needlepoint 14, and three cutting blades 15 continuous from the needlepoint 14 are formed corresponding to the respective corners of the triangle.
With the conventional triangular suture needle 10, the diameter of a sharpened part forming the cutting blades 15 of the triangular prism-shaped part increases it's diameter gradually, and the rest is a triangular prism-shaped part of a constant diameter (parallel part).
Since, with the conventional triangular suture needle, since a round bar is press formed into a triangular prism and the tip is ground to form cutting blades, areas of the circle and the triangle of the triangular prism-shaped part on the needle base side are approximately the same. Therefore, diameter of the fattest portion of the triangular prism-shaped part, namely width of each side of the triangle configuring the cross section of the triangular prism is slightly greater than that of the circular part of the needle base, and is configured as a rounded triangular prism-shaped part. Furthermore, diameter of the cutting blade portion (sharpened part) increasing in diameter is less than that of the triangular prism-shaped part of the parallel part. In other words, the width of the aforementioned respective sides decreases.